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Open Access Publications from the University of California


The concept of the Vertebrate Pest Conference originated in early 1960 from discussions among representatives of the University of California; the California Dept. of Fish & Game; the California Dept. of Agriculture; the California Dept. of Public Health; and the Branch of Predator and Rodent Control, Bureau of Sport Fisheries and Wildlife, U.S. Fish &  Wildlife Service.  The original participants recognized that few published documents on vertebrate pest control were available, as such information was typically contained within in-house reports of the various agencies that were largely unavailable and unable to be cited.  Dr. Walter E. "Howdy" Howard of UC realized that having a conference would permit a Proceedings to be published, in which this information could be made widely available.

To plan such a conference, the organizing group, chaired by Dr. Howard, became the Vertebrate Pest Control Technical Committee, which arranged and hosted the first "Vertebrate Pest Control Conference" held in Sacramento on February 6 & 7, 1962.  The planning committee formally became an incorporated non-profit entity in 1975, and the Vertebrate Pest Conference is now held in late winter or early spring every two years.  It is the most widely-recognized conference of its kind worldwide.

Detailed histories of the development of this Conference are found in these publications:

Marsh, Rex E.  2008.  A History of the Vertebrate Pest Conference.  Proc. Vertebr. Pest Conf. 23:310-326.

Gorenzel, W. Paul.  2004.  Opening Remarks - A Retrospective Look at the Vertebrate Pest Conference.  Proc. Vertebr. Pest Conf. 21:1-2.

Howard, Walter E.  1982.  Twentieth Anniversary of Vertebrate Pest Conferences in California.  Proc. Vertebr. Pest Conf. 10:235-236.

Howard, Walter E.  1962.  Opening Remarks – Vertebrate Pest Control.  Proc. Vertebr. Pest Conf. 1:1-7.


Politics of pesticides

In regard to pesticides, today we have lost the benefit perspective. We no longer have a balance in the mind’s eye of the media, nor in the mind’s eye of the public as a whole. We talk, instead, about the risk to man, the risk to the environment, and the risk to wildlife that is wrought by the very use of the modern tools that have brought up production and health protection miracles. And, until that perspective is re-asserted in a balance, we’re going to lose the very tools that we depend on today to produce quality food, economical fiber, and to protect the good health of this nation. It’s amazing to me that we can ban the use of ethylene dibromide (EDB) and restrict its contamination in ready-to-eat products to 30 ppb, when at the same time we allow aflatoxin, which is a mold in peanut butter, to be present at 15 ppb knowing full well that it has 1,000 times the carcinogenic potential of EDB. That is the consistency and logic of our federal government. We need to re-align perception with fact, because unless we do and until we do, the politics of pesticides are going to win.

Vole control in field crops

There are five species of meadow voles found in California. The two that are most economically important are Microtus californicus and Microtus montanus. Meadow vole populations are extremely cyclic, reaching a peak every four to six years. During these periods when the vole population is increasing in numbers, damage to crops like alfalfa, artichokes, potatoes, and sugar beets can occur. The best time to survey for vole activity is before the crop is planted. The grower or farm operator should look for vole activity in grassy borders around the crop or along roadsides and ditch bank areas. Snap-trapping may also be used to confirm the presence of voles. Clean cultivation and weed control on grassy borders adjacent to crops will help reduce potential harborage for voles. A small or localized vole population on a crop border is much easier to control than if the voles become established in the crop. Rodenticide-treated baits are very effective in reducing vole populations. Bait distribution may be done by spot-baiting, placing bait by hand, or by broadcasting, scattering bait over the entire infested area.

A new concept in pocket gopher control

A new concept in pocket gopher control is advanced which relies on two behavioral traits common to pocket gophers: 1) gophers are quick to invade unoccupied burrow systems when the previous occupant has been killed by a rodenticide; and 2) the invading animal will use existing food stores (i.e., baits) left by the previous gopher. With long-lasting (i.e., durable) baits containing sufficient toxicant, several pocket gophers can be controlled by a single baiting. This new approach assists fn improving gopher control, for control is extended beyond the initial baiting results. Pocket gophers missed in the original treatment or gophers invading from outside areas will continue to be killed for some time following the baiting program. Laboratory and field studies provide supportive evidence concerning the feasibility and practicality of this new concept.

Efficacy of a two-ingredient fumigant on Richardson's ground squirrel

In July 1981, efficacy data were obtained on a new two-ingredient gas cartridge by field testing against Richardson's ground squirrels (Spermophilus richardsonii) in a sagebrush-rangeland pasture. The gas cartridge contained 97 g of a sodium nitrate (65%) and charcoal (35%) mixture and upon ignition generated mainly carbon monoxide with a small quantity of carbon dioxide. We live-trapped 53 (24 male and 29 female) ground squirrels, equipped each with a 164 MHz radio transmitter, and then released each at the point of capture. Later we located each ground squirrel and treated its main burrow and all burrows within 3 m by inserting ignited gas cartridges. After treatment the location of each radio-equipped ground squirrel was plotted. Ground squirrels showing no movement were presumed dead; death was confirmed by burrow excavation. Success rate was 84% as 41 of 50 (18 males and 23 females) died (82%) and 8 survived (16%). The radio transmitter on 1 (2%) failed immediately after treatment. Efficacy was estimated at 83.7%, which exceeds the 70% minimum standard established by the EPA. Thirty-eight ground squirrels died in burrows at depths ranging from 7.6 to 132.1 cm (mean = 74.7 ± SE 5.2 cm), and 3 died in nests at depths ranging from 94.0 to 182.9 cm (mean = 133.0 ±SE 26.2 cm). Seven of the eight survivors were retrapped. Factors contributing to survival are discussed, including soil porosity and moisture content, as well as squirrel body weight. Recommendations for further testing are presented.

Impact of the Belding's ground squirrel, Spermophilus beldingi, on alfalfa production in northeastern California

The Belding ground squirrel (Spermophilus beldingi) is found in rangeland, pasture, and various agronomic crops. However, its impact on agricultural production has been measured only rarely, e.g., by Grinnell and Dixon (1918) and Sauer (1976, 1977). In California, the effects of the Belding ground squirrel appear to be most severe in alfalfa. The present investigations were conducted to measure the impact of the Belding ground squirrel on alfalfa production in northeastern California. Study areas were established on 7 ranches in Modoc County, where rodent exclosure cylinders were placed in alfalfa fields for 44-71 days during growing season before the first hay cutting. Data from alfalfa production indicated Belding ground squirrels reduced alfalfa production by an average of 1,100 lbs per acre (range: 361 - 2,425 lbs/ac) of first cutting alfalfa. Vegetation consumed is probably a very small part of the assessed damage; loss is due to a composite of trampling, runway development, squirrel mounds, vegetation clipping, and forage eaten.

An innovative approach to pocket gopher fumigation

Trials have been done in which pocket gopher (Thomomys bottae) burrows were treated using a U.S. Fish & Wildlife Service gas cartridge followed by fumigation using gasoline engine exhaust fumes from a rototiller with a converted exhaust system fitted with a hose. The exhaust replaced the good air in the burrow system with the lethal carbon monoxide and the smoke fumes from the gas cartridge. The gases are rapidly forced into the far extremities of the runways, as can be detected by slight smoke seepage. The motor is left running for several minutes. The rodents rarely have time to plug their burrows or escape to the surface. We obtained a high degree of control. This method is also effective on ground squirrels in open areas where the soil is relatively moist.

Hazards to golden-mantled ground squirrels and associated secondary hazard potential from strychnine baiting for forest pocket gophers

Radio telemetry and capture-recapture techniques were used to evaluate the hazards to golden-mantled ground squirrels (Spermophilus lateralis) from hand baiting with 0.5% strychnine-treated oats for western pocket gophers (Thomomys mazama) on conifer plantations in eastern Oregon. Toxicology data were collected on field-killed and caged ground squirrels and on caged mink (Mustela vison), great horned owls (Bubo virginianus), and red-tailed hawks (Buteo jamaicensis). Ground squirrel populations were reduced 50 to 75% following underground baiting for pocket gophers. Maximum amount of strychnine alkaloid found in cheek pouches and carcass of a field-killed golden-mantled ground squirrel was 2.88 mg. Mean amount of strychnine in carcasses was 0.35 mg; almost all occurred in the gut. The estimated LD50 for mink was 0.6 mg/kg. The lowest lethal dose for great horned owls and red-tailed hawks was 7.7 mg/kg and 10.2 mg/kg, respectively. The LD50 for owls and hawks was not determined. Long-term effects on golden-mantled ground squirrel populations and secondary hazard potential to owls and hawks were judged to be minimal. Wild mustelids as large as mink could be adversely affected by consuming the gut content of strychnine-killed golden-mantled ground squirrels.

An introductory overview to California ground squirrel control

Techniques for controlling California ground squirrels (Spermophilus beecheyi) include trapping, shooting. acute toxicants, anticoagulants, and fumigants. These techniques are described and compared and the available information on their efficacy and economics is discussed. This kind of analysis is essential if growers are to make logical decisions regarding the various control options.

Efficacy of a number of toxic baits and baiting against the voles, Microtus agrestis and Arvicola terrestris

The results from two series of control experiments against the voles, Microtus agrestis and Arvicola terrestris, are reported. In a series of field experiments in the 1970s, three acute toxicants (zinc phosphide, crimidine, and difluorpropanol) were tested against Microtus. Oifluorpropanol (Gliftor) was found to be the most effective, but no ready-made bait containing it was available. The performance of the crimidine bait (Kastrix) was good enough to fulfill the registration requirements, while the zinc phosphide bait (Myrax) failed to give acceptable results. In the second series (early 1980s) a brodifacoum bait (Klerat) was found to be as efficacious as the crimidine bait (Kastrix) against Microtus, and sufficiently effective against Arvicola, on which the crimidine bait does not work. The experiments with bromadiolone (Arvicolon) and flupropadine (M & B 36,892) against Microtus were discouraging; against Arvicola they were promising, though not yet conclusive. In future research, special attention should be paid not only to the screening of potential toxicants and bait formulations, but also to the study of the basic differences in the reactions of even closely related species to the baits and their active ingredients, as well as to the compensatory demographic responses of the target pest populations in cases of suboptimal performance of the bait in the field.

Rodent control in China

Rodent pest problems and their control in China are reviewed. Three commensal species, Rattus norvegicus, R. flavipectus, and Mus musculus, are important pests both in urban and rural regions. Mus musculus is the most widely distributed species in China. Its population density is cyclic, unique for a commensal species in being found in the arid Xinjiang (Sinkiang) Autonomous Region in Northwest China. In South China, R. losea and Bandicota indica are serious problems in rice and cane fields. Many different genera of field rodents are considered pests to agriculture and/or are reservoirs of rodent-borne diseases. These include Citellus, Marmota, Meriones, Cricetulus, Microtus, Apodemus, Ochotona, Myospalax, Clethrionomys, Sciurus, and Eutamias. The ecology and control of these rodents are included. There are a series of efficient administrative organizations responsible for rodent control. Most campaigns of commensal rodents have relied on a combination of rodenticides and different types of traps, but in the case of field rodents the reliance is heavily placed on poison baits. Diphacinone (Na-salt) is most frequently used for control of commensal species. Zinc phosphide, fluoroacetamide (1081), sodium fluoroacetate (1080), glyftor, and 0.2% diphacinone (Na-salt) are used for field rodent control. Information is supplied on the susceptibility of important rodents in China to different rodenticides, including difenacoum and brodifacoum, and on other means of rodent control.

Acute rodenticides in the control of rodent pest in China: A review

It is said that there are 400 species of mammals in China and 150 species of them are rodents, of which 25-30 species of rodents are usually considered serious pests. Large amounts of grassland, forests, and agricultural crops are destroyed or seriously damaged every year. There is no accurate estimation of the total loss. The first acute rodenticides used for rodent control were white arsenic and yellow phosphorus. These have now been replaced by more suitable chemicals. Acute rodenticides have had a relatively long history of use in China and have played a very important role in rodent pest control. But, at the moment, some of them are becoming a subject of heated dispute and the target of public criticism. Therefore, people follow with interest the development of debate and pay close attention to the future and destiny of acute rodenticides. In this paper, I briefly look back at the history of acute rodenticides used in China and evaluate their achievements and errors.

Rat control in Alberta

A rat control program, administered and coordinated by Alberta Department of Agriculture, has kept Alberta essentially free of Norway rats (Rattus norvegicus) since 1950. A control zone, 29 x 600 km, along the eastern border prevents rats from moving into Alberta from the east. Sporadic rat infestations within the interior of Alberta are reported by concerned citizens and eradicated by government personnel. Strong support for the program by citizens and local governments was developed through public education and information. The program has been successful for a variety of reasons including geography, climate, legislation, availability of warfarin, the relatively small size of the infested area, grass-roots support, lack of complacency, and the personnel involved.

The use of wild carnivore serology in determining patterns of plague activity in rodents in California

Carnivores obtain plague infection through ingestion of infected rodents or rabbits or via flea bite. Most are resistant to infection, show little or no symptoms, and produce antibodies to Yersinia pestis which may persist for several months. Consequently, carnivores can be used as serological plague sentinels using the specific passive or indirect hemagglutination test in the laboratory. A carnivore serology program for plague detection began in California in 1974. The program is a cooperative effort incorporating state and federal vector-borne disease units and state and federal predator animal control personnel. The program has proven to be an important tool in the overall statewide plague surveillance program of the California Department of Health Services, and has been effective in detecting plague over broad geographical areas of the state, as well as in areas heretofore unknown to experience plague activity. Carnivore serology has also proven useful in helping to delineate the extent of plague epizootics, and has given insight into the patterns of enzootic plague among wild rodent populations.

Success in rat control in Kuwait

The preliminary rat survey prior to the actual attack phase of Rat Control Programme in Kuwait revealed an infestation rate with the Norway rat, Rattus norvegicus, in buildings ranging between 32.7%.and 70.7%. The comparatively high infestation was observed in 92.5% of Kuwait buildings. Moreover, the infestation reached 99% in certain districts of the country. This high infestation was associated with an increase in rat-borne diseases particularly murine typhus, salmonellosis rat-bite fever, and certain parasitic diseases. A programme for rodent control in Kuwait was initiated through a political decision by the cabinet which gave the full responsibility of rodent control to the Ministry of Public Health coordinating with other authorities involved in the problem in addition to an independent budget to fulfill all the programme requirements. Financing, administration, guidance, public health information, field work, and research studies were all monitored by the High Committee in addition to Supervising and Following up Committee. The first phase of the programme began in the late months of 1979. It included geographical reconnaisance, survey of rodents and their ectoparasites, establishment of the general plan, and a skeletal organization for the programme. The second phase was the attack phase. It highlighted biological and epidemiological studies, bioassays of pesticides, and training of personnel, which was followed by the actual chemical attack of the incriminated rodents and their ectoparasites for three consecutive years. In addition, sanitation and health education were involved. The third phase, i.e., the maintenance phase, began in August 1982. It is still running to maintain the drastic drop of the Norway rat infestation and to control the house mouse. Kuwait's control programme, based on a scientific basis and with a well-organized administration, has successfully realized 99.7% reduction in the infestation rate, with a 99.6% density of infestation of Norway rats remaining at the end of the attack phase. However, the control of the house mouse produced a reduction of only 71.4% in the infestation rate, and 20% in the density of infestation, possibly indicating intraspecific competition between the two species or less-effective control measures against the mice.

Efficacy of three anticoagulant rodenticides for the control of poison-shy Rattus rattus

House rats (Rattus rattus) which do not consume a lethal dose of zinc phosphide develop poison-shyness after a single exposure. The surviving poison-shy rats cannot be baited again with zinc phosphide for about three months. Poison-shy rats were separately given anticoagulant baits (brodifacoum 0.005%, coumatetralyl and warfarin 0.025%) in no-choice tests. The first two anticoagulants were found to be the most efficient ones. It was observed that those R. rattus which had consumed 56.7 mg/kg or more zinc phosphide died sooner (P < 0.05 to 0.1) after anticoagulant poisoning when compared with normal rats. It is conjectured that prothrombin inhibition is accelerated in the liver of poison-shy R. rattus due to the action of phosphine present in the earlier ingested sublethal dose of zinc phosphide.

Efficacy test protocols for evaluation of ultrasonic rodent repellent devices

Controlled laboratory and field test protocols were developed to assess the repellent efficacies of six commercially manufactured ultrasonic rodent repellent devices. The laboratory test structure (68.7 sq m) was divided into two rooms (32.5 sq m each) with a central harborage area (3.5 sq m) containing a colony of 12 wild Norway rats (Rattus norvegicus). For each test, a single ultrasonic device was attached to the far end of one room and rat activity measures (oat consumption, packet damage, photocell counts) were taken during 1-week baseline and 2-1/2-week test periods. Field test structures varied in floor area (6.5 to 197 sq m) and were of either metal or wood construction. All contained existing Norway rat, house mouse (Mus musculus), or field mouse (Peromyscus maniculatus) infestations. No rodent control was conducted at these sites other than the application of selected ultrasonic devices. Rodent activity (packet damage, food consumption, rodent tracks) was measured twice per week during three successive 3-week intervals with devices operating only during the second interval. Repeated measures analysis of variance and chi square were used to statistically evaluate the reliability of ultrasound effects.

Resistance to the second-generation anticoagulant rodenticides

The second-generation anticoagulants. difenacoum, bromadiolone, and brodifacoum have taken over a considerable part of the rodenticidal market during the last six to eight years. This is partly due to the higher efficiency against a larger spectrum of rodent pest species and partly to the increasing problem of physiological resistance to the older anticoagulants. Resistance of practical importance has, however, now been encountered to difenacoum and bromadiolone in Europe, i.e., UK and Scandinavia. Brodifacoum, in spite of the evidence of a somewhat increased tolerance in some commensal rodent populations, still must be considered a highly effective rodenticide against almost all important rodent pest species. Research leading to the synthesis of similar potent anticoagulant molecules or other slow-acting rodenticides should be encouraged in order to cope with the possible development of resistance also to brodifacoum in the future.

Cholecalciferol: A unique toxicant for rodent control

Cholecalciferol is an acute (single-feeding) and/or chronic (multiple-feeding) rodenticide toxicant with unique activity for controlling commensal rodents including anticoagulant-resistant rats. Cholecalciferol differs from conventional acute rodenticides in that no bait shyness is associated with consumption and time to death is delayed, with first dead rodents appearing 3-4 days after treatment.

The treatment of accidental anticoagulant toxicity in the canine

Anticoagulant poisoning is only one of several causes of hemorrhage in dogs. Hemophilia, von Willebrand's disease, liver diseases, and infections are cited as additional causes of hemorrhage. The duration of anticoagulant activity determines the treatment protocol. The half-life of warfarin is 19 hours; diphacinone, 30 days; brodifacoum, 180 days. The treatment of anticoagulant poisoning requires doses of vitamin K1 at the rate of 5 mg/kg, initially intramuscularly, then orally. Warfarin intoxication is treated for 4 days; diphacinone and brodifacoum for 30 days. Where hemorrhage is present, the prognosis is guarded, and fresh whole blood transfusions are indicated.

Efficacy of brodifacoum (Talon) bait against three rodent species

Brodifacoum was fed to three rodent species, viz . M. hurrianae, R. rattus and F. pennanti, using a no-choice feeding trial for 7 days at various concentrations− 0.005%, 0.0025%, and 0.00125%. The compound was found effective, palatable, developed no sign of poison bait-shyness but indicated a slight aversion of poison. The death of the animals was due to pulmonary distress and hemorrhage.

Commingling of Norway and roof rats with native rodents

The ecology of plague relies on the intermixing (commingling) of animal hosts and their ectoparasites. There has been a noticeable increase in commingling of rats and ground squirrels in Southern California in recent years. This paper discusses this phenomenon in Los Angeles and Orange Counties, where it occurs, how it results from man's activities, and the ecology of varying locations. The role of fleas as vectors of plague and the intermixing of fleas between hosts are discussed. Action to reduce the incidence of commingling and the threat of plague to the urban society is addressed.

A weather-resistant tracking board

The main practical limitation of tracking boards for the study of small mammals is that the sensitive surface is very vulnerable to damage by rain or dew. A tracking board is described that is easily prepared for use in the field, is resistant to rain and running water, and is sensitive enough to record the footprints of mice. The literature on tracking board techniques is reviewed briefly.

Performance of sodium cyanide ejectors

Performance of three models of sodium cyanide (NaCN) ejectors was evaluated at Port O'Connor, Texas, early in 1982. M-44s, M-50s, and coyote getters were test-pulled and reset at 7-day or 21-day intervals for 42 days. Each pull was recorded as good if, in our judgment, it would have taken a coyote. Based on 402 to 430 test pulls of each ejector model, the percentages of good pulls were 40% for M-50s, 73% for M-44s, and 99% for coyote getters. M-44s with shortened plungers performed better than standard M-44s. Most pulls of M-50s resulted in ejection failure due to corrosion between the plunger and ejector body. The greatest problems with M-44s were mechanical defects, particularly of triggers, and caking of NaCN in the capsules. Condition of NaCN was evaluated in 1,354 M-44 capsules that had been weathered for one to six weeks. Eighty-five percent contained normal, dry powder after one week and only 49% were normal after six weeks' exposure. Addition of a beeswax seal decreased capsule deterioration. Based on these results, we recommended that the Service discontinue the M-50 and concentrate on improving the M-44. The Service's Pocatello Supply Depot has shortened the M-44 plunger and added a beeswax seal to M-44 capsules made for use by the Animal Damage Control program.

History and status of predator control in Texas

A historical review of predatory animal damage and the development of the Texas animal damage control (ADC) program is provided, including a discussion of predator species, methods of control and limitations caused by laws, regulations and policies. Recommendations are made for improvements to permit a more comprehensive program with adequate funding, personnel, and control methods.

Toxic characteristics of fluorocitrate, the toxic metabolite of Compound 1080

This paper reviews toxicological research involving fluorocitrate, the toxic metabolite of sodium monofluoroacetate (fluoroacetate), which is the active ingredient in the pesticide Compound 1080. Many toxicological studies have been done with fluoroacetate and the results obtained are actually due to the fluorocitrate because it has been definitely proved that, from a biochemical perspective, fluoroacetate is not toxic but fluorocitrate is. The classical explanation of the toxic action of fluorocitrate is that it inhibits the enzyme aconitase in the tricarboxylic acid cycle. Deactivation of aconitase results in decreased energy production by cells and ultimately death of the organism. However, the more recent explanation of fluorocitrate's mode of action is that it binds with mitochondrial protein which prevents transport of citrate and its utilization by cells for energy production. Metabolism studies indicate that only small amounts, perhaps less than 3%, of fluorocitrate is formed from fluoroacetate. From the limited number of acute and chronic studies conducted with fluorocitrate it does not appear to be as potent as fluoroacetate by either the oral or parenteral routes of administration. This decreased level of toxicity is thought to be due to the larger molecular weight of fluorocitrate which would not be as readily absorbed by tissues. Central nervous system toxic manifestations (i.e., tremors, convulsions) are characteristic in many animals poisoned with fluoroacetate. Fluorocitrate administered directly into the brain was found to be 100 times more toxic than fluoroacetate. The accumulation of citrate in organs is characteristic of fluorocitrate poisoning; from a quantitative point of view the liver is less affected than the brain, heart, kidney, or spleen. Fluorocitrate causes extensive kidney damage, but the testes are most sensitive to sublethal doses. Testicular damage may be either reversible or irreversible, depending upon the dose. Several plants have the ability to metabolize both fluoroacetate and fluorocitrate from either inorganic or atmospheric fluoride.

Biological rationale for 1080 as a predacide

Compound 1080 (sodium monofluoroacetate) is a uniquely selective predacide for controlling coyotes, compared to other predacides. In addition to discussing the biological aspects of 1080, the reasons for the current emotional-political status of 1080 are also reviewed because the biological rationale concerning 1080 has been largely determined by a conspiracy orchestrated in 1972 by an individual of the Council on Environmental Quality but assisted by others from the U.S. Department of the Interior and the Environmental Protection Agency. Many of the distortions about 1080 can also be traced to environmental organizations which still use 1080 as an issue which they can be "anti" in order to solicit funds from the public. This paper is an attempt to clarify the true biological facts about 1080 and to expose the political conspiracies against 1080 by government and environmental organizations.

Repellent or aversive chemicals in sheep neck collars did not deter coyote attacks

Since 1974 the Fish and Wildlife Service has studied a "toxic collar" to poison coyotes that attack collared sheep and goats. The collar patent (McBride 1974) indicates that the same collar could deliver chemicals to repel coyotes, thus saving both the coyote and the livestock. This report summarizes our experience with nonlethal tests of collars. During collar tests with 10 different toxicants, 21 coyotes received sublethal doses followed by aversive behavior or potentially aversive reactions. The subsequent predation history of these coyotes was examined for prey-avoidance. After a sublethal test, all coyotes killed lambs or kids in about 40 days, and 20 of 21 were eventually killed by another toxic collar. Limited testing with coyotes averted to salt flavor by lithium chloride-treated sheep bait also indicated poor protection of live sheep treated externally with salts (NaCl and LiCl). The results indicated little potential for using repellent or aversive chemicals in toxic collars or on sheep to repel coyotes.

Strobe light and siren devices for protecting fenced-pasture and range sheep from coyote predation

The effectiveness of frightening devices for reducing coyote predation on domestic sheep has not been adequately studied. Portable, battery-operated strobe light/siren devices protected pastured sheep from coyotes for a mean of 53 nights (10 trials) and 91 nights (5 trials). Results of ongoing tests of the devices for reducing predation on herded sheep on summer range in western Colorado have so far been encouraging. Future research needs are outlined.

Aldehyde volatiles for use as coyote attractants

This study was designed to evaluate the attractiveness of eight aldehyde volatiles (octanal nonanal, decanal, undecanal, dodecanal, tridecanal, tetradecanal, and hexadecanal) found in sheep liver extract and coyote (Canis latrans) estrous urine to determine their potential for use as odor attractants in predator control. The odors were presented to captive coyotes at the Hopland Field Station and the length of time coyotes responded to the odors was recorded. Octanal, nonanal, decanal, and undecanal all elicited as much sniffing and rub-rolling as did a known coyote attractant, trimethylamnonium decanoate (TMAD). Generally male and female coyotes were equally attracted to the odors; however, nonanal was preferred by males in summer and by females in winter. In comparison to TMAD, some aldehydes were effective in eliciting sniffing and rub-rolling but ineffective in eliciting lick-chewing and biting. Thus, the aldehydes are probably best suited as odor attractants for use with capture devices such as the steel trap, and least suited for use with toxicant-delivery systems such as the M-44.

Predator management for ducks on waterfowl production areas in the northern plains

In 1961, Congress initiated the Accelerated Wetland Acquisition Program, which has resulted in purchase of about 2,450 scattered small Waterfowl Production Area (WPA) management units in the Prairie Pothole Region of Minnesota, Montana, North Dakota, and South Dakota. The WPAs are administered by the U.S. Fish and Wildlife Service (FWS); increased duck production is a major management objective. Duck recruitment rates in much of the four-state area are very low because of high predation, especially on nests. Principal predators responsible for the predation are six mammalian carnivores and one rodent. The actions of predators on WPAs, especially in central and eastern portions of the area, render many areas ineffectual for duck production. A survey of managers of the 22 Wetland Management Districts in the area revealed that little predator management for increased duck production is being conducted on WPAs and that few data are available from which to evaluate effectiveness of methods being used. Public trapping and hunting are permitted on nearly all WPAs. Habitat management is widely practiced but has had limited impact on predation rates. Other predator management activities include limited or experimental use of selective predator control, nesting structures, artificial islands, and electric fences. There is growing demand for cost-effective and acceptable methods to reduce predation, but the number, size, and arrangement of WPAs pose difficult management problems.

Feral equine management at the Naval Weapons Center

Feral equines present a unique management problem for federal land managers. Although feral burros are an invader species introduced onto the North American Continent by 16th Century Spanish explorers, they have both State and Federal protection. Under the umbrella of this protection, feral burro populations exploded in the 1970s. By 1979 the Naval Weapons Center, China Lake, California, was being overrun by burros. Burros were destroying the desert environment and creating very real hazards to aircraft, vehicles and personnel. The Naval Weapons Center in an unprecedented move implemented an interim emergency removal program. A total of 1,513 burros was removed under this program: 864 by live removal and 649 by direct reduction (shooting). Adverse national publicity followed the shooting phase of the emergency removal. Congress had determined in 1971 that wild burros were to be considered an integral part of the natural system of public lands. Had the Navy directly violated this statute? The Navy, beginning with this apparently no-win situation, was able to structure a joint long-term removal program involving the federal government and animal protection groups. Events had been turned around and the earlier no-win situation was now a win-win situation. It has been two years since the long-term removal program was negotiated. An additional 4,387 burros have been removed alive. Burros left on base now number less than 200. The removal of 5,900 burros has allowed the Naval Weapons Center to reintroduce the native ungulate, the Desert Bighorn Sheep. This culminated a four-year effort at the Naval Weapons Center to restore Center ranges to their natural condition.

Nuisance bats: Current technology in their management and control

Managing nuisance bat colonies can be accomplished via exclusion (bat-proofing) or in limited cases via the use of repellents. Exclusion is emphasized as the first and most desirable approach providing it is also practical. New products and devices have recently become available which may significantly aid in making exclusion programs more possible and practical. Repellents such as lights, fiberglass batting, and various improvised mechanical devices may all have some utilization. Controlling nuisance bats can be accomplished via the use of toxicants and trapping, although there is considerable opposition from many bat researchers towards the use of toxicants. Toxicants that have been used against bats include DDT and Chlorophacinone (Rozol®). Efficacy studies conducted on Rozol tracking powder against nuisance big brown bats have demonstrated mean population reductions of 40% within three days, 88% reduction within two weeks, and 98% reductions were obtained within one month following application. It is recommended that toxicants be considered for use only when all attempts at exclusion or repelling the bats have been tried and exhausted. It is contended that professionally supervised and administered toxicant programs are preferable to the various haphazard (and sometimes dangerous) "home remedy" approaches undertaken by a frustrated and a non-educated public. These practices often exacerbate the problem of bat-people contacts as well as subject the bats to excessive inhumane treatments.

Gull exclusion

This paper reports on work carried out in a variety of sites and installations that have required active gull control. The methods used are a result of observations by a variety of researchers and attest to the effectiveness of a behavioral control technique with the use of thin steel spring wire or monofilament fishing line.

Research on winter roosting blackbirds and starlings in the southeastern United States

Each winter, more than 300 million blackbirds and starlings congregate in hundreds of roosting sites in the southeastern United States. In addition to nuisance problems involving odor and property damage from fecal material, and potential airport hazards, research studies to date suggest that the major problems with these birds and their roosts involve grain losses in feedlots, latent disease transmission to livestock, and public health concerns with histoplasmosis. Control methods development studies have shown the utility of Starlicide and nonchemical control methods in reducing starling feedlot problems. A sprinkler-irrigation delivery system for the surfactant, PA-14, has been developed that enhances its usefulness for lethal roost management. Research is being continued to (1) define the behavior and impact of roosting birds on the livestock industry, (2) improve methods of dispersing birds from roost sites, and (3) determine the effect of lethal roost control on subsequent roosting and foraging bird populations.

The white-eyes eradication effort in California

Upon discovery in 1980 in the San Diego area of a feral population of Indian White-eyes (Zosterops palpebrosa palpebrosa), a prohibited species in California, an eradication program was begun by the California Department of Food and Agriculture (CDFA). Mist-netting and shooting proved to be the most successful of the capture methods explored. After three and one-half seasons of retrieval effort and 330 birds taken, fewer than a dozen birds now have been detected in the wild. Within the remainder of the fiscal year, CDFA is conducting intense survey and retrieval. Whether eradication is feasible and applicable to other incipient infestations of exotic birds potentially detrimental to agriculture within the State is yet to be determined.

Preliminary investigations of the effectiveness of trimethacarb as a bird repellent in developing countries

Preliminary information on the effectiveness of trimethacarb as a bird repellent on broadcast seed and ripening crops was obtained during 1982 and 1983 from studies in Haiti, India, the Philippines, Bangladesh, Mali, and the United States. R50 and LD50 determinations for nine pest bird species to cereal crops in these countries indicated birds were not as sensitive to trimethacarb as to the avian repellent methiocarb. Rice and millet seed germination was not inhibited at 0.125 and 0.25% treatment levels. Wheat seed germinated well at treatments of ≤0.5% in Bangladesh. Sorghum seed did not germinate as well at any treatment level. Trimethacarb treatments on broadcast wheat seed in Bangladesh protected exposed seed from bird damage. Field trial demonstrations suggested trimethacarb applications of at least 4 kg a.i./ha to ripening grain are needed to reduce bird damage. Degradation of a 4-kg a.i./ha trimethacarb application on rice and sorghum was rapid with residue levels of 0.10 ppm and 0.68 ppm, respectively, remaining on the seed at harvest. These encouraging results, and the fact that trimethacarb is available in many developing countries, suggest that the chemical should be more extensively evaluated.

Woodpeckers: A serious suburban problem?

Damage to homes and buildings caused by woodpeckers is a widespread and locally severe problem in vertebrate pest control. This paper describes the distribution, characteristics, and impacts of woodpecker damage as determined by questionnaires, interviews, and published accounts. Woodpecker damage results from territorial behavior, feeding, or nesting activity. Some plywood and cedar are especially vulnerable. Average loss per incident is about $300, although some cases result in much greater losses. Disturbance and aggravation are also important factors. Abatement measures include scare devices, structural modification, chemical treatment of the siding, and shooting or trapping (with a permit). Success is variable. Recommendations to reduce the problem include a public awareness program, continued abatement research, a change in plywood production or installation procedures, and a reduction in the effort required to obtain a permit for lethal control.

Current status of research on the blackbird-sunflower problem in North Dakota

Since 1979, the Denver Wildlife Research Center, U.S. Fish and Wildlife Service, has conducted an accelerated research program on the blackbird-sunflower problem which occurs annually in the Dakotas and Minnesota. The objective is to develop effective, cost beneficial, and environmentally safe methods for reducing blackbird damage to ripening sunflower. A multidisciplinary approach involving interrelated studies of problem definition, ecology, and control methods development is being used. Preliminary results are presented from several studies involving: state- and county-wide estimates of damage; frequency distribution and timing of damage; compensatory growth in early damaged sunflower heads; breeding male blackbird censuses; mass-marking migratory red-winged blackbirds (Agelaius phoeniceus) in spring roosts; food habits of red-wings; the chemical frightening agent, 4-aminopyridine; the avian repellent, methiocarb; decoy crops for blackbirds; frightening devices; and bird-resistant varieties of sunflower. Management strategies suggested from these studies are provided.

Potential primary and secondary hazards of avicides

There are six chemicals or groups of chemicals that are currently registered as avicides that can be used in some or all of the U.S. Most of these chemicals, because of their diverse chemical composition and innate toxicological effects, present somewhat different primary and secondary hazards to avian and mammalian predators and scavengers. Of the chemicals reviewed, all appear to present some degree of primary hazard to non-target birds and mammals; however, PA-14, the Starlicide family of chemicals, and fenthion appear to be the least hazardous when used according to use directions. 4-Aminopyridine, endrin, and strychnine, because of their high acute toxicity and lack of selectivity, must be considered potentially more hazardous. With respect to secondary hazards, the ranking of chemicals changes considerably and only PA-14 appears to present a negligible hazard. The Starlicide family of chemicals presents negligible hazards to most animal species under currently registered uses, but may be potentially hazardous to cats and owls under specific use conditions. Two chemicals, 4-aminopyridine and strychnine, are potentially more hazardous to predatory and scavenger animals due to their highly toxic nature and rapid lethal effects in target species, leaving unassimilated chemical in the gastrointestinal tract. The remaining chemicals, endrin and fenthion, have been shown to possess the potential for more significant secondary poisoning; however, because of restrictive uses, most of the potential hazards have been avoided in operational use.

Bird damage chronology and feeding behavior in two sunflower fields, Sacramento, California, 1982

Bird damage was assessed weekly from soon after anthesis until harvest in two sunflower fields in the Sacramento Valley, California, during 1982. Damage chronology was similar at both sites, with damage concentrated in the second to fourth weeks after anthesis when the seeds were in the doughy stage of development. Less than 10% of the total losses caused by birds occurred during the final month before harvest. Overall bird damage was quite low (0.20 and 0.26%) in each field and in one, damage by wind was 2.4 times greater than that caused by birds. Brewer's blackbirds (Euphagus cyanocephalus) and house finches (Carpodacus mexicanus) both occurred in low-to-moderate numbers in one field, while high numbers of blackbirds, mostly red-winged blackbirds (Agelaius phoeniceus) occurred at the other field. At both fields, the numbers of blackbirds recorded peaked during the dough stage of sunflower development, whereas finches were most numerous somewhat later in the damage season. Analysis of the esophagi of 15 red-winged blackbirds collected at one field showed that in addition to sunflowers, various wild grass seeds and insects were consumed.